221B Baby Street
by SilverOcean01
Summary: With Mary dead, John is left to parent their infant daughter. Deciding that it would be for the best, he asked Sherlock if he can move back to Baker Street. How will Sherlock cope with having a child around? And how will John cope with having to look after his daughter and friend? The story of 2 men and a baby in Baker Street.
1. Chapter 1

**Hello everyone! So, a new story I hope you all will enjoy. I started writing this after S3, so that's why the baby's name isn't Rosie, but overall I still like my little girl character, so I'm sticking with her. This work is mostly finished (I think) but I'm still polishing it up a bit. Please leave any questions or comments on my work! I love hearing from you!**

 **Chapter 1**

"I don't understand, John," Sherlock said, staring at his friend in mild confusion. John rubbed at the back of his neck.

"I want to move back in with you. Into Baker Street. If you wouldn't mind," he stated again. Sherlock stood expressionless, blinking a few times before replying.

"What about your infant daughter?"

"Well, she'd come with me. We'd both move in with you," John responded, if a bit hesitantly.

"John, you know I don't cope well with children," Sherlock started, only to be cut short by John.

"I know, but Sherlock. My wife just died bringing my daughter into the world. Granted, she was a...well, challenge, but still. I love my daughter, but I can't stay in that flat another day and with having to care for the baby and everything...it would just be better if we can be here." John sighed and looked at Sherlock pleadingly. "Please Sherlock. Just for a little while? For me?"

Sherlock internally cursed himself for getting so attached to John. He couldn't say no to his best friend. He sighed, being a tad dramatic on purpose, but he nodded.

"Fine. But only until we can find you a better living situation," Sherlock said. John smiled.

"Thank you Sherlock."

Inside, Sherlock couldn't help but feel happy that his best friend and former flat mate was moving back in, but it was tempered by the trepidation of John being joined by his daughter. But he'd already said yes. There was little he could do now without risking his friendship with John. _How bad can it be?_ Sherlock thought to himself.

When John moved in, it was a big day. There was furniture moving and unpacking. John was currently assembling a cot in his old room, as Mrs. Hudson held the baby girl in her arms, cooing over her. Sherlock couldn't help but roll his eyes, disgusted by the baby talk Mrs. Hudson insisted on. Finally, the land lady seemed to realize there were two grown men in the room and addressed them.

"So this'll be the nursery then?" She asked, looking around.

"Yup and my room," John replied with a small smile. Mrs. Hudson seemed a bit surprised.

"Oh? You mean you two won't be..." She trailed off, the implication clear. John groaned.

"For the last time, I'm not gay!"

"It doesn't matter to me, dear," Mrs. Hudson replied. John shook his head, but focused back on assembling the cot. Sherlock watched the proceedings until the baby started to cry, at which point Mrs. Hudson attempt to calm her down by bouncing her slightly.

"I think she's hungry," John said, moving to put what he was working on away.

"No no dear. I've got it. In the kitchen, yeah?" Mrs. Hudson asked. John nodded, adding a "thank you." The land lady just smiled and was quickly out of the room with the wailing baby.

"You could help, Sherlock," John said as he went back to work on the cot.

"Hmm?" The detective asked, not really paying attention.

"You could help me with this, you know. Or help with Cassandra." Sherlock frowned.

"Cassandra?" He asked. John looked up at him.

"You've already forgotten my daughters name, haven't you?" He asked, not surprised but a little annoyed.

"No, I simply failed to listen when you told me," Sherlock replied. "I was thinking about an experiment." John sighed.

"Well, can you please try to remember it this time?" The doctor asked. There was silence from the detective.

"Sherlock!"

"Oh fine. If it will make you shut up about it," he huffed out. John nodded slightly, concentrating on his work. He knew he'd probably have to remind Sherlock again, but at least they were headed in the right direction.

The first few days were rather uneventful. John tried to keep himself and Cassandra out of Sherlock's way, as John had promised. In fact, Sherlock hardly saw John because of a case he was involved in.

When he finally did make it home, he collapsed in his bed from exhaustion, only to wake up hours later to John cooking. Cautiously, Sherlock poked his head out the door, and John smiled at him.

"Want some dinner?" He asked, to which the detective nodded slightly. He couldn't remember the last time he'd eaten, and whatever it was John made smelled delicious. John's smile widened, and he turned around to check on the food. Cassandra was sat in a small chair with toys all around her. She burbled happily as she hit one of them.

"You know Cassandra is the name of a Greek princess, right?" Sherlock asked.

"No, I didn't," John replied.

"Well, a mythological princess. She was said to have been a prophetess, but when she rejected the god Apollo's advances, he cursed her so that no one would ever believe her prophecies. She was said to have prophesied the fall of Troy, but of course no one believed her." Sherlock had been watching the baby as he spoke, and John mused to himself that Sherlock looked like he was trying to deduce her.

"Fascinating. However, my little girl isn't a prophet," John said as he went over and picked up the little girl, bouncing her slightly in his arms. Sherlock scoffed.

"You don't know that. She has yet to speak. And it's prophetess, not prophet. That's the male term," the detective corrected. John rolled his eyes fondly.

"Doesn't matter," he said, and then the kitchen timer started to beep.

"Sherlock? Hold Cassie for me?" John asked, placing the baby in Sherlocks arms without waiting for a response. Sherlocks mouth flapped as he tried to think of how to say no, but his hands held the little human tightly. John quickly tended to the food before turning around to thank Sherlock when he burst out laughing.

Sherlock was holding the baby, but at the end of his outstretched arms with his nose crinkled in disgust as Cassie chewed on her own fist. John calmed himself quickly and took the baby from Sherlock.

"She won't hurt you, you know," John said, a teasing chuckle in his tone. Sherlock scowled at him.

"She's disgusting. Wet and slobbering and...limp. Honestly," Sherlock said, glaring slightly at Cassie who only burbled happily in response. John just chuckled and shook his head, sitting at the table to cuddle his daughter. Sherlock served himself some food and sat as well, though he rather wished he didn't.

"She's just a baby, Sherlock. She can't help it," John said, picking up a bottle he'd heated earlier and started to feed Cassandra.

"She's disgusting. How can you want that?" Sherlock asked. John looked at him with a playful glint in his eyes.

"I put up with you," he said. "And you're way worse." Sherlock looked at him, offended.

"Excuse me? How am I worse than an infant that drools and needs nappies changed every half hour?"

"Let's see. Human body parts in the fridge, that time the bottom of the shower was covered in...what was it again? Eggs? Or the time you made jelly out of pigs blood," John lists off some of Sherlocks more troubling experiments. "And if I remember correctly, I was the one who had to clean up after you on those occasions." Sherlock huffed.

"That was for science. Necessary experiments to prove my theories. Much more important than whatever it is your child is doing." John raised an eyebrow.

"Oh really? I'm raising another human life, teaching it how to live and survive and learn. One day, she may very well be a doctor or a scientist or something else important. Or maybe she'll be the most important of all - someone who saves someone else," John said. "Experiments and science can't save people the way another human being filled with compassion can."

Sherlock was silent, knowing John was right only because Sherlock had experienced it first hand. His experiments had always given him some measure of fulfillment, but when John came along, that's when he finally began to feel important. John had saved him, in a way he couldn't fully describe.

He sighed in defeat, picking at his food. The only sound in the room was Cassie sucking contentedly on her bottle and Sherlocks fork hitting the plate every now and then. John had noticed how quietly Sherlock had accepted his defeat and was rather impressed. He figured Sherlock was just too exhausted to argue with him any longer.

John happily cradled his daughter in his arms, feeding her with a smile. Sherlock ate quietly, watching John and the baby in his arms guzzling back the bottle. Sherlock wrinkled his nose.

"How can such a tiny being eat so much?" He asked. John chuckled.

"She's constantly growing. She needs as much as she can get," he replied. Sherlock didn't seem impressed.

"She's just chugging it."

"Yeah, she does that when she's hungry." Soon enough though, Cassandra pushed the almost empty bottle away, finished with her dinner. John put her over his shoulder, blanket under her as he burped her. The little girls burp maybe Sherlock's eyes widen. John laughed, watching his friend's reaction.

"Disgusting," Sherlock finally muttered. John held his tongue, choosing to smirk instead. The detective stood, dumping his dishes in the kitchen sink, giving one last contemptuous look at John and the tiny human before heading to the living room. Sitting on his black chair, legs folded beneath him and hands clasped in front of him, he drifted off into his mind palace.

He was drawn out of it, to his own surprise, hours later by the cries of Cassie. He frowned, listening as he heard John trying to calm her down, but to no avail.

"Shh, it's alright sweetie, it's okay," Sherlock overheard John say, a little more desperately than usual. He felt bad for his friend. John needed his sleep, as it was tough enough to get it as it was. The child seemed to decrease his rest even more.

Sherlock sighed, deciding to experiment with something. He grabbed his violin and began playing. When John had first lived with him, the ex army doctor had had fitful nights filled with nightmares. Through studies, Sherlock discovered that John seemed to sleep better on the nights he played violin music. Sherlock now wondered if John's offspring would react in kind. So, he played.

It wasn't to long before the incessant wailing of the infant ceased, and Sherlock could just make out John's sigh of relief. Sherlock hoped that John didn't make the connection between Sherlock's playing and the baby's sudden quiet spell, but he kept on playing.

A short while later he could hear John snoring softly in his room, and Sherlock smiled to himself, finishing his piece before going to bed as well.

 **Thpughts? Love it? Hate it? Wondering what rock I've been hiding under? Please, comment!**


	2. Chapter 2

**I'm so sorry everyone. I don't know what went wrong with the first time I posted this. Hopefully this time it will work. Thank you to everyone who let me know there was a problem. Here is the fixed chapter. Enjoy!**

The weeks turned into months since John had moved back into Baker Street, and despite his early apprehension, Sherlock was finding it rather easy to adjust. And regardless of his initial dislike of Cassandra, he grew rather fond of the young girl.

Her bright eyes and generally pleasant demeanour seemed to outweigh her naturally revolting habits. John had even gotten Sherlock to hold Cassandra and feed her a few times, taking care of her so he could have a precious few minutes of respite.

Like now, where Sherlock was entertaining the small girl while John took a much needed shower, stretching it as long as he dare to relax his muscles. Sherlock sat on the living room floor, waving toys in front of Cassandra, who sat on the floor, burbling happily. Sherlock spoke to her, but talked as he did to adults.

"She's perfectly capable of understanding complex speech John," he'd said one day, remarking on John's use of 'baby talk'. "You're only discouraging her development by talking to her in such dumbed down speech."

"She's my daughter and I'll talk to her however I want," John argued. Sherlock rolled his eyes.

"If you've got your heart set on her being ridiculously ordinary, fine," the detective huffed, but no more was said about it.

Currently, while Sherlock played with her, he was explaining the chemical compounds of some of the things around them.

"So that's two hydrogen atoms combined with one oxygen atom to make water," he said, pointing to a glass of water he had. Cassandra squealed and clapped her hand. Sherlock smiled.

"I knew you'd get it. It's rather simple, isn't it?" He said, picking her up and setting her in his lap. Cassie made a babbling noise and Sherlock smiled.

Suddenly, Sherlock's ears picked up the sound of footsteps on the stairs and he stood, Cassie in his arms, instinctively protective. The door swung open and there stood Mycroft Holmes, with a rather pleasingly baffled expression on his face.

"Hello brother mine," he greeted, a tad more hesitantly than normal.

"Mycroft," Sherlock replied simply, while Cassie babbled happily in his arms, looking up at their guest. Mycroft frowned.

"Have I interrupted something? Stepped into an alternate universe, perhaps?" Sherlock couldn't help but grin.

"Of course not. As you know, John has moved back into Baker Street, along with his daughter, Cassandra. Do say hello, Mycroft. It's rude to ignore her so. Mummy would be displeased." Mycroft frowned heavily, looking down at Cassandra, who smiled back up at the grumpy man.

"Hello," he said reluctantly. Cassandra burbled happily. Sherlock stood, holding the baby in his arms as he moved to set her in her play pen before sitting his chair.

"So Mycroft, what are you doing here?" Sherlock asked, clasping his hands in front of him. Mycroft looked at Sherlock in distaste, taking a seat as well.

"Am I not allowed to simply drop in and say hello?" Sherlock hummed.

"Mmm, no. I know you better than that," he replied. Mycroft let out a displeased sigh.

"There is, of course, more to my visit," he said, irked at Sherlock's ease of seeing through him. The younger Holmes cocked a curious eyebrow at his brother as he sat back in his chair, inviting his brother silently to continue. Mycroft sat down stiffly in John's chair before continuing.

"There is a matter of...utmost importance. I request your...help," the elder Holmes said cautiously.

"Really Mycroft, there's no need to beat around the bush." Mycroft rolled his eyes at his brother's impatience.

"This matter includes international security, I am not simply allowed to discuss the matter openly," he snapped. Sherlock cocked his head.

"And who do you imagine overhearing us? John? He will be a part of the investigation, to be sure. Mrs. Hudson? I hardly believe you're worried she'd hear anything, much less repeat it. Or is it little Cassie you're afraid will hear?" He asked, a pleased smirk at his brother's obvious annoyance.

Mycroft pinched the bridge of his nose, closing his eyes for a moment before dignifying his brother with a response.

"Alright, fine. I shall simply have you escorted to my office then, shall I?" The elder Holmes said with an insincere and menacing smile. Sherlock smirked gleefully.

"That's so boring, brother mine. Why don't you simply tell me what you so desperately need me to do for you?" The younger Holmes practically sneered the words. Mycroft was clearly getting frustrated.

"Don't make me force you Sherlock," he warned sternly.

"As if you could," his brother retorted, unfazed by the threat. John appeared at this moment, rubbing his hair dry as he made his way into the living room.

"Hello Mycroft," he said, picking up his daughter from her play pen and cradling her in his arms. "What brings you here?"

The elder Holmes gave him an exasperated look.

"My brother is being a pain, as usual," he replied. "I have a case, but he simply won't listen to me."

John hummed curiously. "Sherlock?" He asked. He had long ago learned that there were always two sides to the Holmes story, and usually neither were the full truth. Sherlock huffed.

"My brother is, as usual, forcing his way into our home only to tell me he needs me somewhere else. I simply refuse to leave until he tells me the details," he replied. John nodded, processing the information.

"Right. Well. Mycroft, why don't you give us a few details about the case and then Sherlock can make an informed decision to follow you back to your office for more. Deal?" He suggested. Though both brothers seemed unhappy at not getting their way, the compromise was eventually accepted.

Mycroft eventually cleared his throat and told them the basic information of the case. Sherlock eventually agreed that he would take it, and arranged to meet Mycroft in his office in an hour. John watch as Mycroft left, smiling at Sherlock when he heard the front door shut.

"Promising," John said, bouncing his little girl happily. Sherlock frowned.

"What?"

"This case. Sounds promising," John said. Sherlock hummed noncommittally, steeping his fingers under his chin for a long moment, eyes falling closer in thought.

Cassandra burbled happily in her fathers lap, and Sherlock's expression softened, ever so slightly, at the sound. John grinned to himself, pleased that his little girl had such an pull over the detective.

"John, you're being ridiculous," Sherlock said, his words clearly reflecting his frustration.

"I'm making sure she's going to be well looked after, Sherlock. If you screw up, she could get hurt, and I will kill you," the blogger replied vehemently. Sherlock's frown deepened.

"I am more than qualified to care for her, you know. And yet you don't trust me to care for her?"

"No Sherlock, that's not what I'm saying. I'm saying that you could put her in harms way, or completely forget about her if you wander off into your mind palace. This is simply a list of things you have to do, and things you must not do under any circumstance, alright?" John said exasperatedly.

He knew this conference was a bad idea, but he had been forced to attend. Which meant leaving Cassie with someone. John's original plan was to let Mrs. Hudson look after the little girl.

But Sherlock had been adamant that he was to watch her. John had reluctantly agreed, but he was still worried. Could Sherlock really be trusted to care for the baby girl? Sherlock let out a groan.

"I would never endanger her, John, nor ignore her. She is my priority during your time away," he said confidently. John gave Sherlock a sceptically look, but sighed, resigning.

"Alright. Just...take good care of her, yeah? And if you need help, call Mrs. Hudson or me."

"Of course John." The father approached his little girl who was laying happily in her play pen.

"Be a good girl for Uncle Lock, okay?" He said, kissing her little head as Cassie smiled, burbling and kicking happily. John gave her a fond smile before standing up and sighing.

"Right, I should go," he said, grabbing his overnight bag. He opened his mouth to say something but decided against it, heading out. Sherlock walked over and picked up Cassie.

"You're father's being silly. I'm perfectly able to care for you. And you know it too, don't you?" He asked. She burbled, wiggling happily in his arms. He smiled.

"I thought so," he said, settling down on the sofa with her, turning on a documentary. Cassie wiggled and moved, eventually settling on chewing on the armrest contentedly. Sherlock frowned, picking up a nearby toy.

"Try this. I don't think your father would like you eating the sofa," he said, giving her the toy. Her eyes widened and she eagerly took the toy, chewing happily on it.

Sherlock settled again with a small smile on his face as he enjoyed the documentary, explaining every once in a while how the narrator was wrong, or elaborating on something to Cassandra.

It wasn't until she started crying that Sherlock realized it had been a while since she had been changed and fed. He set about doing this, heating up her bottle as he changed her, smiling and making faces at her as he did so.

He settled with her on the sofa again, her cradled in his arm as he fed her. She eagerly ate, and Sherlock even burped her. He smiled at her as she settled against him, clearly ready for a nap.

He waited until she was sound asleep before taking a photo of them both, Cassandra sound asleep on his shoulder. He set her in her cot, covering her in a blanket before texting the photo to John with the caption "To prove you wrong. -SH".

John smiled down at his phone, loving the picture and feeling all the more relaxed as he rode the train to the convention. Perhaps this wasn't such a bad idea after all.

 **Love it? Hate it? Finally able to read it? Please let me know!**


	3. Chapter 3

**I'm back! (Finally.) In my defence, it's been a ridiculously busy summer. But here is chapter 3! Enjoy!**

Chapter 3

It's four in the morning and Sherlock is suddenly woken up to a horrific scream.

His eyes fly open as his brain registers Cassie's young voice, and he bolts out of bed to her cot. The poor girl is in tears, crying her heart out. Sherlock scoops her up, cradling her close to his chest as he tries to quiet her.

"There there. I'm here. No need to be upset," he says comfortingly, but the baby keeps crying. He checks her, making sure she doesn't need changing before reaching for a bottle he had prepared earlier. Offering it to her, he smiles softly as she latches on.

But a moment later, she pushes the bottle away, crying even more. The detective frowns, unsure what is happening. He pats her back, bouncing her slightly in an attempt to calm her. He even sings to her, a soft lullaby in his deep voice, holding her tightly. But nothing works. Cassie still cries. Sherlock begins to worry.

What if he did something wrong? What if she was in distress that Sherlock couldn't figure out? He worriedly rocked her, trying to calm her. He pulled out his laptop and started playing some music, hoping that might help.

It was an hour later before Cassie had finally cried herself back to sleep, and Sherlock held her, panicking in silence. He spent the next two hours wide awake and scouring the Internet for anything that might help. He did manage to find a few helpful tips and tricks to help calm Cassie.

One of the most likely suggestions was that she was teething, so Sherlock set about preparing things that might help ease her pain. When she woke up a while later, Sherlock offered her a warm bottle. She drank most of it, before pushing the remainder away. She seemed at peace for the moment, so Sherlock just held her and rocked her. Cassie played happily with a toy he gave her, gumming the rattle-like object with contented sounds. Sherlock sighed, relaxing at the happy girl in his arms.

"Hey Sherlock," John said, his voice coming from the speakers of Sherlock's laptop as he smiled on the screen. That smile soon turned into a frown though as John peered at the screen.

"Sherlock, are you okay?"

The detective tiredly ran a hand through his messy curls. He looked like he hadn't slept in days - bags forming under his eyes, his hair unkempt even for Sherlock, and the drool-stained tee shirt he wore not quite sitting right. Sherlock hummed tiredly.

"'m fine," he said, trying and failing to stifle a yawn. Cassandra sat happily in his lap, burbling as she saw her daddy. John smiled at her.

"Hello baby girl. Daddy will be home tomorrow, I promise," John said, before studying Sherlock again.

"Are you sure you're okay Sherlock? You look awful."

"I'm fine John. I swear," the detective said irritatedly. "Travel safely." With that, he disconnected. Cassandra frowned, looking up at Sherlock.

"Daddy had to go, sweetie. But he'll be home soon," he explained, not quite stifling another yawn. She babbled, apparently moving on. Sherlock relaxed against the headboard, eyes falling shut. It had only been three days, but he felt like it had been an eternity. Having read up on all the tips for teething toddlers, he experimented with Cassandra to see which worked best.

It turned out, aside from having her gums rubbed, Cassandra really liked to chew on a cold teething ring. Luckily for Sherlock, both were rather easy things to do. Unfortunately for him, the pain associated with the teething had Cassandra up almost every hour, meaning Sherlock had to be up as well. This meant that the man who was known to go days without sleep for a case had legitimately been awake for days. And he was not coping well.

John may believe that Sherlock was a machine that needn't eat or sleep, but the truth was that Sherlock was very human. Three days without sleep and caring for a distraught infant had taken their toll on the detective, and he dreaded the remarks his friend would make when he arrived home.

John arrived home the next day. He grabbed his bag, paying the cabbie before digging around in his pocket for his keys. Unlocking the front door, he called up, "Sherlock, I'm home!"

But there was no answer. Worry pricked at the back of his mind, but he pushed it away, rationalizing that Sherlock probably hadn't heard him. John climbed the stairs, calling out again as he opened to door to their flat.

"Sherlock, I'm-." He stopped, then broke out into a huge smile. Sherlock was laying on the sofa, angled slightly towards the back, with Cassie sound asleep on his chest. Sherlock's eyes were closed, his breathing steady as he too slept, arm over Cassie's small body protecting her.

John slowly set his bag down and got out his phone, careful not to make a sound. He took a picture of his daughter and his best friend. After taking a few pictures, he smiled, making his way quietly further into the flat. Sherlock woke several minutes later, hearing John in the kitchen. He instinctively protected Cassie, before relaxing once he knew it was just John. The good doctor came through with two cups of tea, smiling as he saw Sherlock now awake.

"Have a nice nap?" He asked softly, setting Sherlock's cup on the coffee table as the detective cautiously sat up.

"Yes, thank you. When did you get home?" Sherlock asked quietly, holding the sleeping Cassandra to his chest.

"About ten minutes ago." John said with a smirk. Sherlock's face fell slightly.

"Oh. I suppose you saw..." He trailed off. John nodded, sipping his tea.

"You two were quite cute," he replied, smiling at the detective. Cassie shifted in Sherlock's arms, causing the detective to look down at her.

"Was she alright?" The doctor asked. It took Sherlock a moment before he answered.

"She was fine, John. Though I do think she's started teething." The doctor sighed, hand running a hand through his hair.

"Yeah, I knew it wasn't to far away. She's already 4 months old," he said. Sherlock nodded slightly.

"She likes it when you rub her gums. Or give her a chilled teething ring," the detective informed him. "I've found those calm her best." John frowned slightly in surprise.

"You...you rubbed her gums? And bought her teething rings?" The doctor asked, surprised at the level of attention and care Sherlock had given his daughter while he had been away. Sherlock shrugged, as if it was nothing.

"She was in distress. I helped ease the pain," was his plain reply. John just smiled slightly to himself, impressed. He knew Sherlock cared about Cassie more than he cared to admit, but he hadn't known that he cared this much. It made him relax a bit, knowing his daughter had been well taken care of in his absence.

"Thank you, Sherlock," John said with all the gratitude he felt. Sherlock gave him a small smile.

"You're welcome John."

 **Love it? Hate it? Think I need to post more frequently? Let me know with a review!**


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